To determine the appropriate method out of various available methods to measure build-up doses, the measurements and comparisons of depth doses of build-up region including the surface dose were executed using the Attix parallel-plate ionization chamber, the Markus chamber, a cylindrical ionization chamber, and a diode detector. Based on the measurements using the Attix chamber, discrepancies of the Markus chamber were within 2% for the open field and increased up to 3.9% in the case of photon beam containing the contaminant electrons. The measurements of an cylindrical ionization chamber and a diode detector accord with those of the Attix chamber within 1.5% and 1.0% after those detectors were completely immersed in the water phantom. The results suggest that the parallel-plate chamber is the best choice to measure depth doses in the build-up region containing the surface, however, using cylindrical ionization chamber or diode detector would be a reasonable choice if no special care is necessary for the exact surface dose.
Water

We evaluated on the calculation accuracy of treatment planning system (TPS) with phantom having convex and concave surface. The TPS is Eclipse (Varian, USA) using both algorithms AAA and PBC for photon dose calculations. PBC algorithms have three corrections of Batho, modified Batho (M-Batho), and equivalent TAR (E-TAR). The field sizes were 10x10 cm2 and 20x20 cm2, and MLC-shaped fields for these fields. We measured doses at three depths 5, 10 and 15 cm in phantom of SSD=90 cm in the condition of inserted farmer chamber. For given conditions, we have calculated dose with these algorithms and compared them with measured doses. In AAA the calculated doses (dose/MU) were agreed to measured doses within +/-1% in flat and convex surface and were under estimated with -1.9% maximum in concave surface. In PBC the calculated doses were over estimated with +1.7% and +4.1% respectively in flat and convex surface and the differences were from -3.1% to +2.1% in concave surface. In comparison of criteria from AAPM and IAEA reports, and statistical analysis for these results, it is found that the AAA's results are in good agreement with measured values and the M-Batho's results are generally good agreed with measured values among PBC algorithms.
Water

The Comparison of the KAPM Dosimetric Protocol (1990) with the TG-21 and Clambda/C(E) (ICRU-21 and SCRAD protocol) method is studied. The therapetutic range of radiation (photon 4MV-15MV and electron 6MeV-20MeV)and three kinds of the chambers were used in the water phantom. The Results from TG-21 and KAPM Protocol did not show much differences (less than 1%) throughout the whole energy range; N(D) from KAPM protocol and Ngas from TG-21 showed 0.2% deviation mainly from W/e difference between two protocols. But the results from KAPM protocol (1990) and those from Clambda/C(E) Method showed -1.9+/-0.6%(KAPM protocol is higher) deviation for photom beam and +3.3+/-1% (KAPM protocol is lower) deviation for electron beams.
Water

No abstract available.
Water

This study introduced the main water resources for daily accommodation in 3 districts of ¢n Biªn, Hßn §Êt, and T©n HiÖp, including pond and lake water (52.72%), rainy water (42.74%) and drilling well water (4.08%). Some risks of pollution of the water resources such as no filtration and polluted drainage for rainy water, sewage surrounding the drilling well and pollution resources far from the drilling well less than 10 m.
Water Pollution ; water

The information of species and quantity of enteric viruses in surface water, finished water, and tap water is important in helping understand the pathogenesis of viruses, providing information about health and hygiene, improving handling technique of drinking water, and establishing the standards of water quality. Using standard total culturable virus assay-most probable number (TCVA-MPN) method, we tried to detect infectious enteric viruses in surface water, finished water, and tap water samples that were collected and evaluated according to the information collection rule (ICR). The results obtained with TCVA method were compared to the results from both reverse transcription-polymerase chain reaction (RT-PCR) and integrated cell culture-RT-PCR (ICC-RT-PCR) method. Five of 86 samples (5.8%) were positive as determined by the TCVA-MPN method. Two of 86 samples (2.3%) were positive for reovirus as determined by the RT-PCR and ICC-RT-PCR, and contained infectious reovirus. One of 86 samples (1.7%) was positive for coxsackievirus type B3 as determined by the RT-PCR and ICC-RT-PCR.
Drinking Water ; Hygiene ; Water Quality ; Water*

To measure the mutagenic activity of micro-organic pollutants in drinking water, mutagenic test was conducted using Salmnella typhimurium TA 98 strain on the water sample taken from three water supply station and six tap water in Seoul in July and November 1987. The results were as follows : 1. The average amounts of organic matters in raw, treated, and tap water sampled in July were 0.38mg/l, 0.28mg/l, and 0.45mg/l, respectively, and sampled in November were 0.34mg/l, 0.24mg/l, and 0.22mg/l, respectively. The amount of organic matters of tap water sampled in November did not increase while that of tap water sampled in July increased compare to those of raw or treated water. 2. The amount of organic matters is the highest in neutral fraction compare to acidic and basic fractions. 3. In the five out of six tap water and raw water of Paldang and Kuui station sampled in July, the mutagenic ratios were greater than two (both direct and indirect mutagenicity). 4. In the three out six tap water and raw and treated water of Kuui station sampled in November, the mutagenic ratios were greater than two. 5. While mutagenic were low in acidic and basic fraction, they were high in neutral fraction. The samples which had high mutagenic activity in the total amount also showed high mutagenic activity in neutral fraction. 6. While mutagenic activity was decreased after the treatment of water, it was increased in tap water as the distance from the water supply station increases.
Drinking Water* ; Drinking* ; Seoul* ; Water ; Water Supply

PURPOSE: We compared the calculated percent depth dose curves of 6 MeV electron beam to that of measured to evaluate the usefulness of Monte-Carlo simulation method in radiation physics. MATERIALS AND METHODS: The radiation dose values of 6 MeV electron beam using EGS4 code with one million histories in water were compared values that were measured form the depth dose curve of electron beam irradiated by medical accelerator ML6M. The central exis dose values were calculated according the changing field size, such as 5 X 5, 10 X 10, 15 X 15, 20 X 20 cm2. RESULTS: The value calculated showed a very similar shape to depth dose curve. The calculated and measured value of Dmax at 10 X 10cm2 cone is 15mm and 14mm respectively. The calculated value of the surface radiation dose rate is 65.52% and measured one is 76.94%. The surface radiation dose rate has vaied from 64.43% to 66.99. The calculated values of Dmax are in the range between 15mm and 18mm. The calculated value was fitted well with measured value around the Dmax area, excluding build up range and below the 90% depth dose area. CONCLUSION: This result suggested that the calculation of dose value can be replace the direct measurement of the dose for radiation therapy. Also, EGS4 may be a very convenient program to assess the effect of radiation dose using by personal computers.
Microcomputers ; Water

Absorbed dose to water based protocols recommended that plane-parallel chambers be calibrated against calibrated cylindrical chambers in a high energy electron beam with R50>7 g/cm2 (E> or =16 MeV). However, such high-energy electron beams are not available at all radiotherapy centers. In this study, we are compared the absorbed dose to water determined according to cross-calibration method in a high energy electron beam of 16 MeV and in electron beam energies of 12 MeV below the cross-calibration quality remark. Absorbed dose were performed for PTW 30013, Wellhofer FC65G Farmer type cylindrical chamber and for PTW 34001, Wellhofer PPC40 Roos type plane-parallel chamber. The cylindrical and the plane-parallel chamber to be calibrated are compared by alternately positioning each at reference depth, zref=0.6R50-0.1 in water phantom. The DW of plane-parallel chamber are derived using across-calibration method at high-energy electron beams of 16, 20 MeV. Then a good agreement is obtained the DW of plane-parallel chamber in 12 MeV. The agreement between 20 MeV and 12 MeV are within 0.2% for IAEA TRS-398.
Electrons ; Water

PURPOSE: It is difficult to exactly determine the surface dose and the dose distribution in buildup region of high energy X-rays by using the conventional ion chamber. The aim of this study is to evaluate the accuracy of widely used dosimetry systems to measure the surface dose and the depth of maximum dose (dmax). MATERIALS AND METHODS: We measured the percent depth dose (PDD) from the surface to the dmax in either a water phantom or in a solid water phantom using TLD-100 chips, thimble type ion chamber, diode detector, diamond detector and Markus parallel plate ion chamber for 6 MV and 15 MV X-rays, 10 10 cm2, at SSD=100 cm. We analysed the surface dose and the dmax. In order to verify the accuracy of the TLD data, we executed the Monte Carlo simulation for 6 MV X-ray beams. RESULTS: The surface doses in 6 MV and 15 MV X-rays were 29.31% and 23.36% for Markus parallel plate ion chamber, 37.17% and 24.01% for TLD, 34.87% and 24.06% for diamond detector, 38.13% and 27.8% for diode detector, and 47.92% and 36.01% for thimble type ion chamber, respectively. In Monte Carlo simulation for 6 MV X-rays, the surface dose was 36.22%, which is similar to the 37.17% of the TLD measurement data. The dmax in 6 MV and 15 MV X-rays was 14~16 mm and 27~29 mm, respectively. There was no significant difference in the dmax among the detectors. CONCLUSION: There was a remarkable difference in the surface dose among the detectors. The Markus parallel plate chamber showed the most accurate result. The surface dose of the thimble ion chamber was 10% higher than that of other detectors. We suggest that the correction should be made when the surface dose of the thimble ion chamber is used for the treatment planning for the superficial tumors. All the detectors used in our study showed no difference in the dmax.
Diamond ; Water